Vandals have defaced a monument to victims of a World War Two attack against Jews in Poland, covering it with racist inscriptions and swastikas in green paint.

A 2001 Polish investigation concluded that the Jedwabne pogrom was inspired by Poland's then-Nazi occupiers and the case remains a traumatic memory for Jews and many Poles today.

The latest incident, which has been condemned by the Polish government, is the latest in a series of racist and xenophobic acts of vandalism targeting the small Jewish and Muslim communities in eastern Poland as well as the tiny Lithuanian minority.

At least 340 Jews were burned alive by their Polish neighbours in a barn in the 1941 campaign in the eastern town of Jedwabne.

The site was later turned into a memorial.

Vandals also smeared a wall surrounding the memorial with signs saying "I'm not sorry for Jedwabne" and "They were highly flammable". They obscured the Hebrew and Polish signs on the memorial itself with paint.

Poland's interior ministry said that it was likely that all the recent anti-Semitic and xenophobic incidents were perpetrated by the same people,

Foreign Minister Radoslaw Sikorski condemned the act of vandalism as "alien to Polish tradition."